using (AttributeDefinition acAttDef1 = new AttributeDefinition())
{
acAttDef1.SetDatabaseDefaults(bt.Database);
acAttDef1.Verifiable = true;
acAttDef1.Prompt = "Number";
acAttDef1.Tag = "Number";
acAttDef1.TextString = "0";
acAttDef1.Height = 1;
acAttDef1.Justify = AttachmentPoint.MiddleCenter;
acAttDef1.Position = new Point3d(20.0, 0, 0);
acAttDef1.AlignmentPoint = new Point3d(20, 0, 0);
acAttDef1.AdjustAlignment(bt.Database);
acAttDef1.Layer = "0";
btr.AppendEntity(acAttDef1);
bt.UpgradeOpen();
bt.Add(btr);
tr.AddNewlyCreatedDBObject(btr, true);
}